Human papillomavirus (hereinafter referred to as “HPV”) is a virus that causes a papilloma. HPV is classified into 100 or more subtypes. Among the HPV subtypes, common gene regions are known to be preserved. HPV (integrated HPV) integrated in genomic DNA, and HPV (episomal HPV) in the state of a double-stranded circular DNA, occur in cells infected with HPV. It is known that HPV occurs often as integrated HPV in cancer tissues such as tissues of cervical intraepithelial neoplasia occurring the uterine cervix and tissues of oral cancer. Accordingly, the detection of integrated HPV in a cell collected from a subject is important in examining the cancerous state of the cell.
Peitsaro et al. (Journal of Clinical Microbiology, 40, pp. 886-891 (2002)) and Arias-Pulido et al. (Journal of Clinical Microbiology, 44, pp. 1755-1762 (2006)) describe methods of judging the integration of HPV16 in the genomic DNA of a cell with a quantitative real time PCR. Specifically, the DNA amount of an E2 gene region of HPV16 and the DNA amount of an E6 gene region of HPV16 are first measured and their measurements are compared. On the basis of the comparison result, the integration of HPV16 DNA in the genomic DNA of a cell is then judged. The E2 gene region is a region that is often cleaved due to the integration of HPV16 DNA in the genomic DNA. According to the methods described in Peitsaro et al. and Arias-Pulido et al., the presence or absence of the integration of HPV16 in the genomic DNA can therefore be judged on the basis of a variation in the amount of the DNA in the E2 gene region.
However, there is a case where in integration of HPV16 in the genomic DNA, HPV16 DNA is not cleaved in the E2 gene region. Accordingly, even if HPV16 DNA has been integrated in the genomic DNA of a cell, the variation in the amount of the DNA, caused by cleavage of the E2 gene region, may not occur. Accordingly, the methods described by Peitsaro et al. and Arias-Pulido et al. are not accurate enough to detect the integration of HPV16 DNA in the genomic DNA of the host cell.
Steenbergen et al. (Cancer Research, 55, pp. 5465-5471 (1995)) describe a method of detecting the integration of HPV16 DNA in the genomic DNA by fluorescent in situ hybridization (FISH).
However, FISH is complex in operation and requires skills. Accordingly, the integration of HPV DNA in the genomic DNA cannot be easily detected.